1. Field of the Invention
The invention relates to a two-wheeled inverted pendulum vehicle and a control method therefor and, more particularly, to a technique for controlling a two-wheeled inverted pendulum vehicle in which a control system is duplexed.
2. Description of Related Art
In a vehicle described in Japanese Patent Application Publication No. 2009-187561 (JP 2009-187561 A), a motor has a plurality of redundant windings, and the motor is allowed to be driven from a plurality of power amplifier control units. The vehicle includes the plurality of power amplifier control units and a plurality of processors connected to the plurality of power amplifier control units via a system bus. Thus, the control system is multiplexed. If any one of the processors fails, the vehicle is controlled on the basis of an output of the processor other than the failed processor. However, when the motor has multiple windings as described above, cost increases.
The applicant of the present application found problems described below at the time of studying a two-wheeled inverted pendulum vehicle that provides a reduction in cost. The following description was newly studied by the applicant of the present application, and is not the one illustrating an existing art.
FIG. 15 is a block diagram that shows the configuration of a control system in a two-wheeled inverted pendulum vehicle 400 in which motors 407, 408 each have a single winding and the control system is duplexed into a first-line control system and a second-line control system. FIG. 16 is a view of the schematic configuration of the two-wheeled inverted pendulum vehicle 400 in the case where the motors 407, 408 each have a single winding and the control system is duplexed into the first-line control system and the second-line control system.
As shown in FIG. 16, the motors 407, 408 are respectively controllable from only the control systems corresponding to the motors 407, 408 between the duplexed control systems. Microcontrollers 401, 402 respectively control the motors 407, 408 via inverters 403, 404 so as to keep an inverted state on the basis of outputs from attitude angle sensors 411, 412. The microcontrollers 401, 402 respectively control the motors 407, 408 in a feedback manner on the basis of outputs from rotation angle sensors 409, 410.
The operation of the two-wheeled inverted pendulum vehicle 400 in the case where there occurs a failure in one of the control systems in the above configuration will be described with reference to the flowchart shown in FIG. 17. Here, description will be made on the case where the first-line control system has failed between the first-line control system and the second-line control system.
When the first-line microcontroller 401 has detected a failure in the first-line control system (S101), the first-line microcontroller 401 turns off a first-line relay 405 (S102). That is, the first-line inverter 403 is isolated from the motor 407, and the motor 407 enters a free state. The first-line microcontroller 401 outputs information about the failure of the first-line control system to the second-line microcontroller 402.
The second-line microcontroller 402 detects the failure of the first-line control system on the basis of the information from the first-line microcontroller 401 (S103). When the second-line microcontroller 402 has detected the failure of the first-line control system, the second-line microcontroller 402 controls the motor 408 via the inverter 404 such that the vehicle speed of the two-wheeled inverted pendulum vehicle 400 is decreased. That is, it is possible to stop the two-wheeled inverted pendulum vehicle while executing inverted control over the two-wheeled inverted pendulum vehicle from the remaining control system. However, in this case, inverted control over the two-wheeled inverted pendulum vehicle 400 is executed by driving only the motor 408 from the second-line control system. Therefore, the body of the two-wheeled inverted pendulum vehicle 400 turns about an axis that coincides with the free first-line motor 407 (S104). After the vehicle speed of the two-wheeled inverted pendulum vehicle has sufficiently decreased, a rider of the two-wheeled inverted pendulum vehicle is allowed to get off (S105).
In this way, in the case where the motors 407, 408 each merely have a single winding to have a simplified configuration in order to reduce cost, if there occurs a failure in one of the control systems and, accordingly, the two-wheeled inverted pendulum vehicle is caused to stop, the two-wheeled inverted pendulum vehicle turns. That is, it is not possible to keep straight line stability, with the result that it is not possible to cause the two-wheeled inverted pendulum vehicle to stably travel and bring the vehicle to a stop state. However, in the two-wheeled inverted pendulum vehicle, it is required to ensure the stability of control.